Researchers have provided a new and data-driven answer to an important question: how many tree species exist on Earth? The international group has used an extensive global ground-source database to estimate that 64,100 species of trees are known but statistically, there should be much more.
Reporting in Proceedings of the National Academy of Sciences, researchers think there are 9,200 species yet to be found, which would bring the total number of species to 73,300. Calculating this finding was far from easy. The 150 scientists had to identify almost 40 million trees to create this comprehensive database.
“Extensive knowledge of tree richness and diversity is key to preserving the stability and functionality of ecosystems,” lead author Professor Roberto Cazzolla Gatti, from the University of Bologna, said in a statement. “Until today, our data regarding wide areas of the planet was very limited and based on field-observation and lists of species covering different areas. These limitations were detrimental to a global perspective on the issue”.
Limited financing for such a global census, logistical hurdles, field-work struggles, and even taxonomic issues like working out if similar organisms belong to different species or not meant this research was not for the faint-hearted.
Once the mapping of known species was completed, statistical analysis was conducted using the supercomputer at the Forest Advanced Computing and Artificial Intelligence (FACAI) Laboratory of Purdue University in Indiana (USA). That’s where the total estimation of the trees came from, and the discovery that around 14 percent of all tree species appear yet to be discovered.
“We combined individual datasets, coming from someone going out to a forest stand and measuring every single tree, into one massive global dataset of tree-level data. Counting the number of tree species worldwide is like a puzzle with pieces spreading all over the world," explained Professor Jingjing Liang, coordinator of the GFBI Purdue-Hub. "We, the Global Forest Biodiversity Initiative (GFBI), solved it together as a team, each sharing our own piece.”
Among the unknown species, the team expects 40 percent to be found in South America, specifically in two environments: “tropical and subtropical forests” and the “grasslands, savannas, and shrublands” of the Amazon and the Andes. Even more specifically, 3,000 species will be rare and populate these endangered tropical and subtropical regions.
The results show the global variety of trees at a continental and regional scale and highlight the impact that humanity has had on them.
“These results highlight the vulnerability of global forest biodiversity to anthropogenic changes, particularly land use and climate, because the survival of rare taxa is disproportionately threatened by these pressures,” said co-author Professor Peter B. Reich from the University of Minnesota.
Given the changes humans are causing to the global climate, we might lose some of these species before we actually discover them.